Message-Id: <9503210827.AA24178@st.unocal.com>
From: stssram@st.unocal.com (Bob Myers)
Date: Tue, 21 Mar 1995 00:27:22 -0800
In-Reply-To: hazel.2@postbox.acs.ohio-state.edu (Paul W Hazel)
To: baidarka@imagelan.com
Subject: Re: Paddling...
On Mar 21, 1:05, Paul W Hazel wrote:
} Subject: Re: Paddling...
> As Bob pointed out, lift and drag are perpendicular to one another -
> therefore the only way that the vector sum of the two forces can be
> perfectly horizontal (or perfectly vertical, for that matter) is if the net
> value of one of these forces is exactly zero.
> Otherwise, that added value will pull the vector away from a perfect 90
> degrees (horizontal).
Wait a minute - lift and drag are perpendicular, but do not necessarily
align with horizontal and vertical. The only time that would occur is
during the part of the stroke when the paddle is moving directly horizontal
or vertical. If your stroke has a vertical component, you can have both
lift and drag and zero vertical force.
> The point here is that it's not a good idea to try to get perfect horizontal
> force, because then you lose the benefit gained by adding the two vectors.
Huh? What possible benefit is there to a vertical force?
(Kirk actually already answered this in email - lifting the boat a bit out
of the water. But I don't believe this is significant - how much vertical
force can you generate, compared to the weight of the boat+kayaker+load?
Keep in mind that that vertical force is transmitted through your arms to
the boat. How much of your weight do you support with your paddle?)
> For this argument, I assumed a more or less conventional paddle and stroke,
> i.e. the paddle is pulled through the water more or less horizontally with
> respect to the surface for most of the stroke. I have only seen a modern
> "wing" paddle once, and I have never seen it in use. The forces on it will
> be the same of course, but I'm guessing that a different frame of reference
> might be necessary for analysis.
I claim you want little or no lift with a "conventional paddle and stroke",
as you have defined them. To get any benefit from lift, it's got to be
aligned with the direction of motion.
-- Bob Myers Unocal Tech. & Ops. I. S. Support Internet: Bob.Myers@st.unocal.com P. O. Box 68076 Phone: [714] 693-6951 Anaheim, California 92817-8076